Nanosecond laser shock detonation of nanodiamonds:from laser-matter interaction to graphite-to-diamond phase transition

Nanodiamonds(NDs)have been widely explored for applications in drug delivery,optical bioimaging,sensors,quantum computing,and others.Room-temperature nanomanufacturing of NDs in open air using confined laser shock detonation(CLSD)emerges as a novel manufacturing strategy for ND fabrication.However,the fundamental process mechanism remains unclear.This work investigates the underlying mechanisms responsible for nanomanufacturing of NDs during CLSD with a focus on the laser-matter interaction,the role of the confining effect,and the graphite-to-diamond transition.Specifically,a first-principles model is integrated with a molecular dynamics simulation to describe the laser-induced thermo-hydrodynamic phenomena and the graphite-to-diamond phase transition during CLSD.The simulation results elucidate the confining effect in determining the material’s responses to laser irradiation in terms of the temporal and spatial evolutions of temperature,pressure,electron number density,and particle velocity.The integrated model demonstrates the capability of predicting the laser energy threshold for ND synthesis and the efficiency of ND nucleation under varying processing parameters.This research will provide significant insights into CLSD and advance this nanomanufacturing strategy for the fabrication of NDs and other high-temperature-high-pressure synthesized nanomaterials towards extensive applications.

Mode couplings of a semiconductor nanowire scanning across a photonic crystal nanocavity

The position-dependent mode couplings between a semiconductor nanowire(NW)and a planar photonic crystal(PPC)nanocavity are studied.By scanning an NW across a PPC nanocavity along the hexagonal lattice’sΓ– M and M– K directions,the variations of resonant wavelengths,quality factors,and mode volumes in both fundamental and second-order resonant modes are calculated,implying optimal configurations for strong mode-NW couplings and light-NW interactions.For the fundamental(second-order)resonant mode,scanning an NW along the M– K(Γ– M)direction is preferred,which supports stronger light-NW interactions with larger NW-position tolerances and higher quality factors simultaneously.The simulation results are confirmed experimentally with good agreements.

Beyond mirroring:multi-version disk array with improved performance and energy efficiency

Performance and power consumption are two important design objectives for data centers consisting of thousands or tens of thousands of disks （or disk arrays）. To leverage the two objectives, in this study we propose a multi-version disk array （MDA）. The main idea of MDA is to exploit the I/O workload characteristics to guide the replication strategy by replicating multiple versions of the popular data blocks and simply offioading the write data to the free space of the reserved version region, thus achieving high performance in the burst period and low power consumption in the idle period. Our prototype implementation of MDA and the performance evaluations show that the performance of MDA outperforms that of traditional RAID10 by up to 34.4% and 42.3% in terms of the average response time for the online transaction processing （OLTP） application I/O and search engine I/O, respectively. Moreover, the energy efficiency of MDA outperforms that of RAID10 by up to 48.7% and 36.4%, respective to the aforementioned measures.